In any trading market, there is a fundamental fact: one party's gain must correspond to another party's loss. Money does not appear out of thin air, nor does it automatically disappear; it only flows between participants. Just like the conservation of energy in physics, the total amount of funds in the market remains constant, only the allocation constantly changes.

From the perspective of individual participants alone, this is indeed a zero-sum game. The money Zhang San earns is the money Li Si loses, and vice versa. The overall benefit is redistributed, but the total amount remains unchanged.

The reality is far more complex. There is a key role in the market—the market maker or platform operator. They are not passively watching funds circulate among traders; they have their own interests and demands.

Take a certain pair trading as an example. Suppose a popular asset is about to release important data, and the market expects a trend to emerge. The platform will adjust the price labels accordingly. For example, setting a buy price at 1 and a sell price at 1.9 (this is the bid-ask spread). This means that if you go long and your trade succeeds, investing 100 yuan can yield 190 yuan; but if you are wrong, you will lose the entire 100 yuan.

Theoretically, the bullish and bearish traders each make up half. Imagine 100 traders participating, each investing 100 yuan. 50 choose to go long, and 50 choose to go short.

No matter how it ends, the platform needs to pay the 50 profitable traders 190 yuan each, for a total payout of 4,500 yuan. At the same time, it collects the full principal of 100 yuan from the 50 losing traders, totaling 5,000 yuan in income. The platform nets 500 yuan.

The key point: markets with intermediaries are not purely zero-sum. Earning less and losing more—this is the pattern that participants ultimately discover. In the long run, most retail traders end up paying for the profits of the platform or a few institutions. Understanding this mechanism is essential to stay clear-headed in trading.